// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
//
// Slice is a simple structure containing a pointer into some external
// storage and a size.  The user of a Slice must ensure that the slice
// is not used after the corresponding external storage has been
// deallocated.
//
// Multiple threads can invoke const methods on a Slice without
// external synchronization, but if any of the threads may call a
// non-const method, all threads accessing the same Slice must use
// external synchronization.
#pragma once

#include "base/AFPlatform.hpp"

namespace ark {

// Copy from leveldb project
// @see https://github.com/google/leveldb/blob/master/include/leveldb/slice.h

class AFSlice
{
public:
    using value_type = char;

public:
    // Create an empty slice.
    AFSlice()
        : data_("")
        , size_(0)
    {
    }

    // Create a slice that refers to d[0,n-1].
    AFSlice(const char* d, size_t n)
        : data_(d)
        , size_(n)
    {
    }

    // Create a slice that refers to the contents of "s"
    AFSlice(const std::string& s)
        : data_(s.data())
        , size_(s.size())
    {
    }

    // Create a slice that refers to s[0,strlen(s)-1]
    AFSlice(const char* s)
        : data_(s)
        , size_(strlen(s))
    {
    }

    // Return a pointer to the beginning of the referenced data
    const char* data() const
    {
        return data_;
    }

    // Return the length (in bytes) of the referenced data
    size_t size() const
    {
        return size_;
    }

    // Return true if the length of the referenced data is zero
    bool empty() const
    {
        return size_ == 0;
    }

    // Return the i-th byte in the referenced data.
    // REQUIRES: n < size()
    char operator[](size_t n) const
    {
        assert(n < size());
        return data_[n];
    }

    // Change this slice to refer to an empty array
    void clear()
    {
        data_ = "";
        size_ = 0;
    }

    // Drop the first "n" bytes from this slice.
    void remove_prefix(size_t n)
    {
        assert(n <= size());
        data_ += n;
        size_ -= n;
    }

    // Return a string that contains the copy of the referenced data.
    std::string ToString() const
    {
        return std::string(data_, size_);
    }

    // Three-way comparison.  Returns value:
    //   <  0 if "*this" <  "b",
    //   == 0 if "*this" == "b",
    //   >  0 if "*this" >  "b"
    int compare(const AFSlice& b) const
    {
        const size_t min_len = (size_ < b.size_) ? size_ : b.size_;
        int r = memcmp(data_, b.data_, min_len);

        if (r == 0)
        {
            if (size_ < b.size_)
            {
                r = -1;
            }
            else if (size_ > b.size_)
            {
                r = +1;
            }
        }

        return r;
    }

private:
    const char* data_;
    size_t size_;
};

inline bool operator==(const AFSlice& x, const AFSlice& y)
{
    return ((x.size() == y.size()) && (std::memcmp(x.data(), y.data(), x.size()) == 0));
}

inline bool operator!=(const AFSlice& x, const AFSlice& y)
{
    return !(x == y);
}

inline bool operator<(const AFSlice& x, const AFSlice& y)
{
    return x.compare(y) < 0;
}

} // namespace ark
